Transformer construction



April 9, 1957 s. P. PAPPAS 2,788,499

TRANSFORMER CONSTRUCTION Original Filed Nov. 4, 1954 INVENTOR fiat-7s H P4 PPAS ATTORNEYS TRANSFORMER CONSTRUCTION George P. Pappas, Phillipsburg, N. 1., assignor to New York Transformer Co., Inc., Alpha, N. J., a corporation of New Jersey Continuation of application Serial No. 466,755, November 4, 1954. This application May 23, 1956, Serial No. 586,866

2 Claims. (Cl. 336-84) My invention relates to a transformer construction and in particular to the type of transformer in which a unitary coil assembly is embraced in a core of so-called E or F laminations, defining two slots for opposed legs of the coil. This application is a continuation of my copending application Serial No. 466,755, filed November 4, 1954.

It is an object of the invention to provide an improved construction of the character indicated.

t is another object to provide a transformer construction with improved means for dissipating heat.

It is a further object to provide a more efficient transformer construction.

It is a specific object to meet the above objects with a construction which can handle greater loads per unit volume of assembled transformer, thus permitting achievement of a given load capacity with reduced consumption of important materials.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification, in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

Fig. l is a view in perspective of an assembled transformer incorporating features of the invention;

Fig. 2 is an enlarged view in elevation, partly broken away and in section in the plane 2--2 of Fig. 1; and

Fig. 3 is a view similar to Fig. 2 and showing a modification.

Briefly stated, my invention contemplates achievement of important economies of parts and materials in a transformer construction of the character indicated by so closely fitting all parts of the assembly together that airpocket formation within the assembly will be reduced to an absolute minimum. The parts may be so strongly compacted to each other that heat conduction from the interior of the assembly is promoted. The interior of the assembly may be vacuum-potted with a heat-conducting material, thereby achieving the best possible heattransfer coefficient from the interior of the coil slots to the outer surface of the transformer.

In Figs. 1 and 2, the invention is shown in application to a transformer assembly comprising a stack 10 of core laminations, with two end bells 11--12 covering the otherwise exposed parts of coil means 13; the end bells may be of pressed steel. The core 10 may be of the threelegged variety defining two coil-receiving slots 14 between legs 16-17-18. The core assembly may thus comprise a stack of E-laminations, the ends of the E" being closed after assembly of the coil to the core; alternatively, like stacks of F-laminations may be matched to each other after assembly of the coil to one-half of the core. After assembly of the coil means 13 to the core stack 10, the outer exposed legs of the coil means 13 will cover center core leg, thus exposing the remainder or rim of the face of each outer lamination.

nited States Patent O In accordance with the invention, maximum heat transfer from the inner parts of the transformer, for radiation at end bells 11-42, is achieved by closely compacting the coil means within the slots 14 and within at least one of the end bells. This may be done by pre-assembling the coil 13 closely to the dimensions of the slots 14-15, at least for the case of the opposed legs 15 which fit the slots. It is also desired that the other opposed legs 1920 of the coil means 13 shall closely lie over the outer laminations 21-22 of the stack 10 and, to facilitate such fit at the inner corners of the coil, I have shown the outer laminations 21-22 as being formed with slightly enlarged slot openings 14, the center legs 17 thereof being shortened to define recessed corners, as at 23.

As indicated generally above, at least one of the end bells, say the end bell 11, is formed closely to the contour of the exposed part of the adjacent leg 19 of coil means 13. In fact, this contour-fitting portion is preferably so made with respect to the depth of the peripheral flange 24 for said end bell 11 that, upon assembly as by tightening the core bolts 25, the pocket of the end bell 11 will firmly compress the coil leg 19 against the inner wall of the end bell 11 and against the outer surface of the lamination 21. The drawing shows a similar formation and relationship for the end bell 12 with respect to the core leg 20, and this relationship is held by the threaded engagement of the bolts 25 with the flange 26 of the lower end bell 12.

In accordance with another feature of the invention, further improvement in heat transfer may be achieved by vacuum-potting the described constructions with a heat-conducting polymerizable material. In the drawings, I have indicated (by sectioning for plastic) that the potting intimately fills all possible voids, however slight, within the assembly and thus promotes intimate solid heat-transferring contact from the inner confines of the transformer to all outer surfaces. I have found highly satisfactory heat conduction and efficient operation to be achieved when employing a potting of filled resin. Suitable filled resin may include a polyester vehicle with inert mineral filler, such as finely divided slate, silica, talc, mica, or the like.

In Fig. 3, I show a slight modification which may be said to resemble the construction of Fig. 2 in all respects, except that a core band 30 continuously overlaps the outer exposed parts of the sub-assembly comprising the coil and the core; the core band 30 may be of copper, and the overlapping ends of the core band are preferably soldered at 31 to assure permanent electrical conduction and to promote efficient collapse of stray flux. The intimate contour-formed relation of the parts is still preferably as described in connection with Fig. 2, but of course the potting of heat-conducting material intimately fills primarily the space to the inner wall of the core band, and primary reliance is made on direct mechanical contact of the end hell with substantially the entire exposed surface of the core band to promote heat transfer to the end bell.

It will be seen that I have described an improved transformer construction featuring superior heat dissipation, whereby greater temperatures and heat stresses may be tolerated within the volume of the transformer, for a given size of transformer. This means that a given power rating may be achieved with a shorter stack of laminations, thus effecting economies in the cost of laminations and in the length of wire required for the coil means. For a particular transformer constructed as described, and potted with slate-filled resin, I have found that a saving of approximately 30 percent in lamination material is possible over previous constructions in which the end bell is not tightly fitted or contoured to the coil,

Patented Apr. -9, 1 957 ing slots. therebetween',. coil means closely encircling the center leg, and substantially filling said slots, whereby on assembly of said coil means to said core means parts of said coil means project beyond the planes of the outer facesof outer laminations of said stack, thereby exposing peripherally continuous rims of the outer faces of said outer Iamihati'ons; a first metal end bell including flange means in peripherally continuous adjacency with one of said rims and' in close adjacency with the adjacent projecting part of said coil means, a second metal end bell including flange means. in peripherally continuous adja= cency with the other of" said rims and overstanding the adjacent projecting part of said coil. means, and a single solid potting of heat-conducting material intimately and continuously" permeating said coil means and intimately 3 and continuously contacting both said core means and the-inner walls 015 said end bells, said. potted heat-conducting material comprising a polyester vehicle with inert mineral filler.

2. A transformer according to claim 1, and including an electrically conductive core band of substantially the width of said coil means and encircling the outer exposed limit of said c'ore means and of said coil means and in close contour-fitting; relation therewith and in flux-ooh lapsi'ng relation therewith, said core band being covered by said end bells and being in intimate and continuous contact with said potting within said end bells.

References Cited in the file of this patent UNITED STATES PATENTS 1,647,372 Pressley NOV. 1, 1927 1,763,114 Wermine lune 10, 1930 1,988,734 He'l'gason Jan. 22 1935 2,141,141 Kongst'ed Dec. 20, 1938 2,553,362 Dannenberg' May 15, 1951 2,542,733 Tritle et a1; Feb. 20, 1951 2,553,666 McKe'chnie" May 22, 1951 2,572,590 Bjorklund Oct. 23, 1951 

